Lab 5: Interrupts

Advanced interrupt handling and real-time programming techniques for responsive embedded systems

Overview

Lab 5 focuses on advanced interrupt handling and real-time programming techniques essential for responsive embedded systems. This lab teaches students about interrupt service routines, priority management, and real-time system design principles.

Learning Objectives

Understand interrupt mechanisms and vector tables
Implement interrupt service routines (ISRs)
Design priority-based interrupt handling systems
Master real-time programming techniques
Handle multiple concurrent interrupt sources

Step-by-Step Procedure

1. Interrupt System Setup

Configure interrupt vector table and priority levels
Set up interrupt enable registers and control bits
Initialize interrupt sources (timers, GPIO, UART, etc.)
Test basic interrupt functionality

2. Interrupt Service Routine Design

Implement efficient ISR functions
Handle interrupt context saving and restoration
Design minimal processing in interrupt context
Implement proper interrupt acknowledgment

3. Priority Management

Configure interrupt priority levels
Handle nested interrupt scenarios
Implement priority-based task scheduling
Test interrupt preemption and nesting

4. Real-Time System Integration

Integrate interrupts with main program flow
Implement real-time task scheduling
Handle timing-critical operations
Optimize system responsiveness

Technical Implementation

The interrupt system implements priority-based interrupt handling with efficient service routines and real-time task processing. Key technical aspects include:

Vector Table Management: Proper interrupt vector configuration and handling
Priority Control: Hierarchical interrupt priority management
Context Management: Efficient register saving and restoration
Real-Time Processing: Time-critical operation handling

Performance Optimization

Critical optimization techniques for interrupt handling: - Minimal ISR Processing: Keep interrupt service routines as short as possible - Efficient Context Switching: Optimize register save/restore operations - Priority Optimization: Balance interrupt priorities for system performance - Memory Management: Efficient use of stack and global variables

Testing and Validation

Functional Tests

Interrupt Triggering: Verify all interrupt sources trigger correctly
Priority Testing: Confirm interrupt priority and preemption behavior
Nesting Test: Test nested interrupt handling
Timing Test: Measure interrupt response times

Performance Tests

Latency Measurement: Measure interrupt response latency
Throughput Test: Test interrupt processing throughput
Stability Test: Extended operation under interrupt load
Resource Usage: Monitor stack and memory usage

Troubleshooting Guide

Interrupts not triggering:
- Check interrupt enable registers and configuration
- Verify interrupt source configuration
- Test interrupt vector table setup
- Check global interrupt enable status
Priority issues:
- Verify interrupt priority configuration
- Check for priority conflicts
- Test interrupt preemption behavior
- Review priority assignment strategy
System instability:
- Check stack overflow conditions
- Verify proper context saving/restoration
- Test interrupt nesting limits
- Review ISR processing time

Resources and Documentation

E155 Labs Overview
Lab Specs (Placeholder for actual lab specs)
Microcontroller Interrupt Reference Manual
Real-Time Systems Design Guide

Expected Outcomes

Upon successful completion of Lab 5, students will have mastered advanced interrupt handling techniques, implemented priority-based interrupt systems, and designed real-time responsive embedded systems. This foundation is essential for complex embedded applications requiring precise timing and event handling.